The present application generally relates to innovations and improvements in vehicle suspensions. More particularly, the present application relates to a frame hanger and associated vehicle suspension that provides for thrust angle alignment of an axle in a vehicle, and may be useful in multiple axle (i.e., tandem or tridem) on-off highway truck applications, or be applied to a single axle, such as a 4×2 commercial vehicle.
The centerline of a vehicle may be viewed as a line drawn through the midpoint between the wheels on a front axle and midpoint between the wheels on a rear axle. The direction of thrust of the vehicle, or the thrust line, is normally perpendicular to a position of the rear axle; although with an independent rear suspension, the thrust line is a line derived by splitting the toe angle of the rear wheels on the vehicle. Thus, the thrust line refers to the direction of vehicle thrust.
Ideally, the thrust line and the vehicle centerline coincide and are in alignment with each other. However, given the size of the vehicle, manufacturing tolerances, stresses, and component wear, the vehicle centerline and the thrust line often are not aligned, resulting in a thrust angle. The “thrust angle” is the angle between the centerline of the vehicle and the direction of thrust, or thrust line. In order to align the thrust angle, the orientation of the front and/or rear axle with respect to the vehicle frame may be adjusted. Prior designs have utilized square U-shaped shims to adjust the thrust angle at the connection of a bar pin at the walking beam, effectively changing the thickness around the bar pin at the walking beam. This method could be used to adjust the thrust angle; however, it also had the undesirable effect of adjusting the pinion angle of the axle. As a result, adjustments to the thrust angle in these circumstances could require further adjustments to the pinion angle of the axle, resulting in additional time, effort, and cost expended during vehicle set up.
Consequently, there is a need to provide a way to adjust the thrust angle alignment of an axle on a vehicle that does not also result in a change of the pinion angle of the axle. In other words, it would be desirable to provide a vehicle suspension that could be used to adjust align an axle with the direction of thrust, without affecting the pinion angle of the axle. Thus, there is a need to provide thrust angle alignment of an axle independently from adjustment of the pinion angle of the axle.